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Topic: Mysteries (Read 1326 times)

Okay, forget the GI issue - I cracked it and found where the problem was. I'm sorry if I offended anybody with my rantish post.Today, I've got two mysteries for you. If you can, please answer these questions:

1. How come that the sun is shinning THROUGH a ROCK in this render fragment if the RECEIVE SHADOWS FROM SURFACES option in the atmosphere tab is turned ON!?2. Why the f...lowers the rock tower in the picture does not cast ANY shadows on the clouds below, despite it being just a standard terrain feature?!

It is a part of the terrain Oshyan, as can be seen in the right picture. Tower (crater shader), Tow disp. (power fractal shader) and Tower Strata (S&O shader) are the ones responsible for this terrain feature. I made it more or less according to this tutorial I've seen before:

I also tried to move sun beyond the terrain that came before that tower and the sun disc was not visible as it should be. So in theory the "receive shadows from surfaces" option works... but not for that tower... All cloud layers have that option checked as well.

I don't know if the shadow-throwing and sunray-through need a compute terrain to get its exact bearings, so was it a normal setup? Perhaps a tgd would give some folks a chance to see what's happening... but it sounds weird.

I don't know what you mean by "normal setup". Anyway, according to the tower tutorial two "compute terrain" are needed because otherwise you DO NOT get any displacement on the tower surface. At least not using this method.

I'm not an expert Ulco, but if shadows and sunray-through did not require any special actions to be taken like you say, there would be no need for the "receive shadows..." option... Still, it just doesn't work with this rock tower...

I had a similar problem 1-2 months ago but it was only a test that i didn't bother to investigate further.

I tried some options in the render settings today. One option was "Do ray traced shadows" in the "More" tab of the Render node.Have a look if it is checked or not accidentally. The sun shines through the ground even if you have "Receive shadows from surfaces" on in the Atmo node if the "Do ray traced shadows" is OFF.

I will look at it Kadri, so thank you. Usually "Receive shadows" is just enough to hide the sun beyond terrain (it even says so in the atmo tab as well!) and I know that because I've tried it many times before. This is really very disappointing.

For now, however, I decided to use displaceable spheres as rocks. They cast proper shadows, obscure sun as they should and frankly, offer more diversity than the rock tower created from a crater. Unfortunately, you cannot really successfully use the S&O shader on them, because strata goes across the whole sphere in every possible direction... Not just horizontally. But it is a good solution and I may post some pictures later.

I will use displaceable spheres to create rock towers and this solution is far more versatile, plus controlling this feature is easier. You can have a look at it below. I guess it's nothing new for you... But maybe it's good to have some solutions/posts refreshed once in a while.

As you can see, all of the rocks that constitute this tower (there are three of them) are casting proper shadows on the terrain and clouds below. They also obscure the sun's disc as they should. The bottom part of the highest "sprock" is also roughly displaced, while the top has larger, smoother displacement features. Displacement is distributed according to the altitude with the use of a simple "distribution shader" setup. Darkened version of Dune's Parkwood Grass is also included at the top. It looks somewhat "physics defying" but make no mistake - it greatly comes down to what you want to create. I needed this kind of arrangement.

The only disadvantage of this method is that if you want to have several towers like this and populate them, say, with pines... you have to create pine population for each of the spheres. I don't think you can populate several separate objects at once to reduce the number of populations in use. Here is one more shot for a better view with sun illuminating the surface: